Improvement in truss-bridges



T W. PRATT.

improvement in Truss-Bridges.

Patented April 25.1871.

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T. WILLIS PRATT, OF BOSTON, MASSACHUSETTS.

Letters Patent No. 114,039, dated April 25, 1871.

lMPROVElVlEN'I'- IN TR USS-BRIDGES,

The Schedule referred to in these Letters Patent and making part of thesame.

To all whom it may concern V Be it known that I, T. WILLIs PRATT, ofBoston, in the county of Suffolk and State of Massachusetts,

have invented certain Improvements in the Gonstruo Figures 4,5, 6, and 7detail and modifications to bereferred to.

My invention consists, first, in a peculiar connection of the strutand'tensiou-braces with each other and the upper and lowe chords of abridge, in which the iron employer of channel form and My inventionconsists *lx-boudly, in the application of one or more plates to .achjoint or point of connection of the 'st'rg't and tension-braces with theupper and lower'chords, for the purpose ofaddiug strength at the pointswhere the said braces are connected with the chords.

To enable others skilled inthe art to understand and use my invention, Iwill proceed to describe the manner inwhich I have carried it out.

In the said drawing-- A represents the upper chord of a bridge, thechord being formed of iron, either cast or wrought, of channel form,well known to be that shown in'fig. 4, in which the iron is so shapedthat a flange, 'a is produced below and at right angles to each side ofthe horizontal portion 1), the flanges a being parallel, or nearly so,to each other.

This channel iron may be made in one piece, fig. 4, or be composed oftwo pieces of angle-iron riveted directly together, (fig. 5 or of twopieces of angleiron connected by a plate, fig. 6.

B represents the lower chord, of a form similar to that A.

The upper and lower lower chords A B are connected and fastened, byrivets c or otherwise, to strutbraces G and tension-braces D, likewisemade of iron, of channel form-the strut-braces (I being those whichincline from the upper chord downward and away from the center of thebridge, and the tension-braces D being those which incline from theupper chord downward and toward the centeroi the bridge. Thestrut-braces may, however, be formed of I-shaped iron, fig. 7.

The upper and lower ends (I e of the tension-braces are so bentinopposite directions as to fit snugly under and upon, and lie parallelto, the upper and lower chords AB, the upper and lower ends M of thestrutbraces 0 being also bent in opposite directions, as shown insection, fig. 2.

The upper ends or portions 71. of the strut-braces G are madetofitsnugly under the upper ends or portions (1 of the tension-braces D,while the lower ends or portions '2 of the strut-braces O fit snuglyupon the lower ends e of the tension-braces D, through which they areriveted to the upper and lower chords A B.

EEare flat metal plates, placed one at each side of the joints or pointsof connection of the tops of the braces G D with the upper chordB.

Each plate E is placed inside the flange a so as to shed water, and isriveted thereto at It, the plate being also riveted, at Z, to theflanges a of both the strut and tension-braces.

G G are plates similar to those (E) riveted, at m, to the outside of theflanges a of the lower chord B, the plates G being also riveted, at n,to the flanges a of both the strut and tension-braces, by whichconstruction the bond between the braces and chords is still furtherincreased and strengthened; the joints which otherwise would be somewhatflexible being thereby rendered rigid, as requiredwhere the bridge is tosup port a, weight in notion. T g

The beams supporting the floor of the bridge may be laid either upon thetops of the upper chords B, or upon the tops of the plates G, the spacebetween these plates in either case being covered or filled up toprevent exposure to the Weather.

It will be seen, from the foregoing, that a tensile strain is exerted onthe braces D, which, at their upper ends, (I, is converted into ahorizontal thrust in the direction of or toward the center, as indicatedby the arrow 10, while, at their lower ends, e, the horizontal strain isexerted in a direction from the center toward the ends of the bridge, asindicated by the arrow 11.

The upper and lower chords, as well as the braces, may be curved insteadof straight, if desired; but I find it more econo'rnicaland convenientto make them straight, as shown.

I-shaped or double-channel iron, fig. 7, may be used in the constructionof triangular trussbridges, instead of iron of single-channel form, fig.4, if desired, without departing from the spirit of my invention.

Claims.

What I claim as my invention, and desire to secure by Letters Patent,is-

' described and shown, strut and tension-braces G D,

1. The peculiar method herein shown of connectand chords A B, the wholeconstructed and operating the strut and tension-braces G D'with theupper ing as and for the purpose set forth. and lower chords A B in theconstruction of triangu- Witness my hand this 8th day of February, A. D.lar truss-bridges, substantially in the manner and for 1871. the purposedescribed. I Witnesses:

2. The combination of the plates E G, formed as N. W. STEARNS,

W. J. CAMBRIDGE.

T. WILLIS PRATT.

